In Situ Strain Evolution and Performance Analysis of Fiber Prestressed Composites During Curing Process

Curing stresses at the fiber-matrix interfaces in carbon fiber-reinforced polymer (CFRP) components are critical factors governing the initiation and propagation of internal defects, which ultimately lead to structural failure. Fiber prestressing introduces compressive stress at the fiber-matrix interfaces by pre-stretching fibers, thereby regulating the in-plane stress distribution and enhancing load-bearing performance. However, the influence of prestress on stress evolution and its underlying mechanisms remains insufficiently understood, hindering accurate determination of optimal prestress parameters and process optimization. In this study, a multi-field coupled finite element model for the curing of fiber-prestressed composites is established, and an experimental platform with an online monitoring system is developed to investigate curing strain evolution and mechanical strengthening mechanisms under different prestress levels. The results show that prestress effectively modifies the internal strain distribution and significantly increases the residual compressive strain in CFRP laminates by improving fiber alignment uniformity and resin infiltration within fiber bundles. At a prestress level of 0.010, the flexural strength, flexural modulus, and tensile strength increase by 7.83%, 18.81%, and 12.73%, respectively. Furthermore, prestress alters the residual stress state of the aircraft wing skin, reducing compressive stress from −21.14 to −26.92 MPa, thereby markedly improving mechanical performance and service reliability.